1. Field of the Invention
The present invention relates to an ink ribbon cartridge for use with a dot printer, a daisy wheel printer, a thermal printer and other printers as well as various kinds of typewriters and reciprocally fed to use upper and lower parts thereof in sequence. The present invention relates also to a color ink ribbon accommodated in such a ribbon cartridge which is detachably loaded in any of various kinds of printers, particularly a serial color thermal printer.
2. Discussion of the Background
Usually, a disposable ink ribbon housed in an ink ribbon cartridge for use with a thermal printer or like printer allows only a very small number of characters to be printed out due to the limited total length of the ribbon, requiring frequent replacement of the ribbon. Increasing the ribbon length which may be contemplated to solve the above problem brings about another problem that the diameters of pancakdes which the ribbon forms are increased, resulting in the need for a bulky ribbon cartridge.
To settle the above-stated dilemmatic situation, there has customarily been used a ribbon which has a width great enough to accommodate at least two characters and has upper and lower portions which are each defined along the length of the ribbon to be used in sequence. A prior art ribbon cartridge, therefore, has right and left portions configured symmetrically to each other. At first, an ink ribbon accommodated in such a cartridge is fed in one direction to print out data using its upper or lower portion. After the whole upper or lower half has been used up, the cartridge with the ink ribbon kept thereinside is turned upside down and, then, the ink ribbon is fed in the other direction to print our data using the other portion of the ribbon. The problem with this kind of ribbon cartridge is that since guide rollers for guiding the ink ribbon and a feed gear and a pressure gear coactive for feeding the ink ribbon are arranged in the cartridge, opposite shoulder portions of the cartridge are substantially protruded outwardly to make the whole cartridge bulky. Another problem is that since the ink ribbon is guided by way of those shoulder portions, it has to travel a substantial distance between a ribbon feed position and a print position where a thermal head is located and between a ribbon takeup position and the print position, wasting a considerable proportion of the ribbon length.
Meanwhile, where such an ink ribbon cartridge is applied to a serial color thermal printer or like printer, an ink ribbon received in the cartridge is usually provided with a color ink pattern consisting of a yellow (Y) region, a magenta (M) region and a cyan (C) region each of which extends over the whole width of the ribbon. This three-color pattern repeats itself throughout the length of the ribbon. In operation, such a color ink ribbon is fed in one direction at first to use its upper portion and, in this instance, the colors appear at the print position in a pattern or sequence of "YMC". However, while the ribbon is fed in the other direction to use its lower portion after turning over the cartridge, the colors appear in a pattern or sequence of "YCM" which is different from the previous pattern of "YMC". To print out data in purple, for example, it is the usual practice to print out magenta (M) first and, then, cyan (C) from above the magenta (M). After the cartridge has been reversed, however, cyan (C) is printed out first and, then, magenta (M) from above cyan (C). Purple attained by printing out cyan (C) over magenta (M) and purple attained by printing out the latter over the former are delicately different in tint from each other. Such is undesirable from the printout quality standpoint.
It is not impossible to cause cyan (C) to be printed out over magenta (M) even after the ribbon cartridge has been turned over. This is not without cost, however. Specifically, such an implementation would use two different patterns in printing out one line of data and, thereby, halve the effective number of characters per unit length of the ribbon when the ribbon cartridge is turned over.